Process for the production of methacrylonitrile

ABSTRACT

A process for the production of methacrylonitrile in high yields by vapor-phase catalytic ammoxidation of isobutene comprising the use of a catalyst containing as the active component a composition having the empirical formula Fe10W1-30X0.01-15Me0.015O12-143 wherein X represents at least one element selected from the group consisting of P, B and Te, and Me represents V and/or Mo.

United States Patent Saito et al. 1 1 Jan. 7, 1975 1 1 PROCESS FOR THEPRODUCTION OF 3,254,110 5/1966 Sennewald C181. 260/4653METHACRYLQNITRILE 3,433,823 3/1969 McMahon 260/4653 {75] Inventors:Shigern Saito, Tokyo; Jun lshikura; FORElGN PATENTS OR APPLICATIONSYutaka Sasaki both of Yokohama 3844717 8/1963 Ja an 260/4653 Monya,Karlagawai Takash' 41-3616 3/1966 163m 260/4653 lmada, Yokohama all OfJapan 41-6897 4/1966 Japan 260/4653 g ee C emical Industry Co. JapanTokyo, Japan [22] Filed: Man 13, 1972 Primary E.raminerloseph P. Brust121] Appl. No; 234,345

. [57] ABSTRACT 1 1 Foreign Application Priority Data A process for theproduction of methacrylonitrile in Mar, 21, 1971 Japan 4613098 highyields by vapor-phase catalytic ammoxidation of isobutene comprising theuse of a catalyst containing [52] L'.S. Cl. 260/4653 as the activecomponent a composition having the em- [51] Int. Cl C070 121/02 'piricalformula Fe W ,X Me O wherein [58] Field of Search 260/4653 X representsat least one element selected from the group consisting of P, B and Te,and Me represents V [56] References Cited and/or M0 UNITED STATESPATENTS Yasuhara et a1 260/4653 3 Claims, N0 Drawings PROCESS FOR THEPRODUCTION OF METHACRYLONITRILE BACKGROUND OF THE INVENTION 1. Field ofthe Invention This invention relates to a process for the production ofmethacrylonitrile by vapor-phase catalytic ammoxidation of isobutene.The object of the invention is to carry out the above-mentioned reactionfavorably by the use of a catalyst exerting a commercially efficientcatalytic activity with respect to the formation of methacrylonitrile byammoxidation of isobutene.

2. Description of the Prior Art As for ammoxidation of olefins, thereare many reports with respect to the production of acrylonitrile byammoxidation of propylene, whereas very few reports regarding theproduction of methacrylonitrile by ammoxidation of isobutene. Propyleneand isobutene are extremely different in reactivity in oxidationreactions, especially in the ammoxidation reaction. Therefore, there areencountred many difficulties in favorable production ofmethacrylonitrile, as commonly indicated in publications such as US.Pat. No. 3,346,617 and Japanese Patent Publication No. 7771/1966. Otherknown processes for the production of methacrylonitrile are such asthose in Japanese Patent Publication No. 26390/1964, US. Pat. No.3,461,150 and Japanese Patent Publication 7774/1967.

These processes. however, have some commercial problems unsolved,regarding to low conversion to methacrylonitrile or short duration ofthe activity. I

SUMMARY OF-THE INVENTION As a result of extensive investigations toovercome these disadvantages, we have found a novel catalyst compositionwith along duration of the activity and a vary high conversion tomethacrylonitrile. The present invention is based upon the finding asmentioned above.

As characteristic features of this invention particularly advantageousfrom theindustrial point of view are mentioned high selectivity ofmethacrylonitrile under high conversion of isobutene withoutintroduction of steam into the reaction system and duration of the highactivity fora long period of time, low by-production of methacroleininclined 'to make troubles in the recovery and purification systems ofthe product, low byproduction of acetonitrile and low combustion of NHDESCRIPTION OF THE INVENTION The catalyst used in this invention is anoxide composition containing iron, tungsten and at least one elementselected from thegroup consisting of phosphorus, boron and tellurium.Other elements contained in the composition are vanadium and/ormolybdenum. Proportions of the elements in the composition is alsocritical and compositions beyond the range as specifiedbelow will resultin reduction of the activity or in much decline of durability of theactivity.

This invention is concerned with a process for the production ofmethacrylonitrile which comprises con-' tacting a mixture of isobutene,molecular oxygen and ammonia in vapor phase with a catalyst containingas the effective component a composition having the empirical formula FeW X Me O wherein X represents at least one element selected from thegroup consisting of P, B and Te, Me represents at least one elementselected from the group consisting of V and Mo and the suffix a, b, cand d are atomic ratios in such ranges that 1 a 30,0.015 b 15,0.01 c 5Sand d is a number corresponding to oxides formed by com bination of theabove-cited compounds which equals from 12 to 143.

The catalyst with the above-mentioned composition is prepared by anyknown method. It is especially preferable that all the components areintimately mixed. The exact chemical structure of the materialscomposing the catalyst is uncertain and the above-cited empiri calformula is given as a result of analysis.

The starting material for providing the iron component in the catalystmay be selected from a variety of materials. For example, ferrous oxide,ferric oxide or iron oxide in the form of co-existing ferrous and ferricoxides may be employed. Alternatively, materials which finally afford astabilized oxide of iron after subjected to chemical or calcinationtreatment may be used. As the materials of this nature are mentionediron salts of inorganic acids such as iron nitrate and chloride, andiron salts of organic acids such as iron acetate and oxalate. Thesematerials may be calcinated either after neutralization with an alkalisuch as ammonium to iron hydroxide or directly to yield iron oxide. Inaddition, iron hydroxide or metallic iron may be used. The metallic ironmay be treated with heated nitric acid. In this case the iron isconverted to ferric nitrate. Regardless of the starting material it ispreferable to mix inti' mately with other components and it ispreferable to add the material in such a form of fine powders, aqueoussolution or sol.

The starting material for the tungsten component may be anywater-soluble or -insoluble tungsten compound. For example, tungstentrioxide, tungstic acid, ammonium para-tungstate, ammoniummeta-tungstate, tungsten halides and the like. As in the case of iron,caution of intimate mixing with other components applies as well.

The starting materials for the phosphorus or boron component may beselected from a wide variety of compounds that supply these elements. Itis more common to add the'material in the form of phosphoric or boricacid.

As the tellurium component may be employed any water-soluble or-insoluble tellurium compound. For example, tellurium dioxide, tellurousacid or telluric acid may be used. Alternatively, metallic tellurium maybe used. It may be used as it is in powdery form or after its oxidationwith heated nitric acid.

Any water-soluble or -insoluble vanadium compound may be used for thevanadium component. For example, vanadium pentoxide, ammoniummeta-vanadate, vanadyl oxalate or vanadium halides may be employed.

The molybdenum component may come from any watersoluble or -insolublemolybdenum compound. For example, molybdenum trioxide, molybdic acid,ammonium para-molybdate, ammonium metamolybdate, molybdenum halides andthe like may be employed.

The catalyst exerts excellent activities without carrier but it may beused in combination with an appropriate carrier, which is advantageouslycontained in a proportion from 10 to by weight of the entire catalyst.As the carrier may be used silica, alumina, zirconia, magnesia,silica-alumina, silicon carbide, alundum, inorganic silicate or thelike. Any additives for improving physical properties of the catalystsuch as binding agent may be added, if desired, unless it arisesunfavorable effect. These additivessuch as carrier or binding agent maybe optionally added regardless of the composition unless they do notcause remarkable changes in the characteristic features of the catalystof this invention described herein above and in examples below. Thecatalyst containing such additives should be regarded as the catalyst ofthe present invention.

The catalyst of the invention may be employed either in the form ofpellet in the fixed-bed reaction or in the form of powder in thefluidized-bed reaction.

The catalyst of this invention is prepared by mixing the startingmaterials in such a way as giving the predetermined composition, dryingand calcining the same. Conditions under which calcination is conductedare important for providing the resulting catalyst with de siredactivities It is preferable to heat the catalyst in the presence ofoxygen at a temperature from about 400C. to about 950C. for a periodfrom 2 to 48 hours.

As the feed gas are used a hydrocarbon, ammonia.

and oxygen, said hydrocarbon being substantially composed of isobutene'.Nitrogen, steam or carbon dioxide may be simultaneously supplied as thediluent gas.

Air is preferably used as the oxygen source but a gas substantiallycomposed of oxygen may also be used.

, I The molar ratios among the components of the feed gas are important;the oxygen to isobutene molar ratio is preferably from 1:1 to 5:1, andthe ammonia to isobutene ratio from 1:1 to 5:1.

The reaction temperature is preferably in the range from 300C. to 500C.From theoperational point of view the reaction is preferably conductedunder around atmospheric pressure, but, if necessary, it may beconducted under elevated or reduced pressure. When the reaction isconducted under elevated pressure,-the pressure is preferably below 5-kg./cm. G. Suitable contact time is from 0.1 to 20 seconds and a contacttime of from about 0.5 to about seconds produces especially goodresults. Contact time as referred to herein is defined by the followingequation.

Contact time (sec) Apparent volume of the catalyst: (liter) Total volumeof the feed gas at the reaction temperature supplied in a unit time[litcr/sec.]

lncarrying out the process of this invention either a fixed-bed reactoror a fluidized-bed reactor usually used for vapor-phase catalyticreactions can be employed.

Recovery of the desired product is effected by washing the reaction gaswith water or an appropriate organic solvent. Purification is feasibleby known distillation procedures.

DESCRIPTION OF PREFERRED EMBODIMENTS Examples of the catalyst accordingto this invention and the ammoxidation reaction of isobuten'e using saidcatalyst are shown below. In order to demonstrate the characteristicfeatures of the invention, comparative examples are also given.

EXAMPLES AND COM PARATIVE. EXAMPLES Test methods of the catalyst are asfollows:-

A. Activity test by the fixed-bed reaction A U-type reactor having 16mm. in inner diameter and 500 mm. in-length was filled with 20 ml. ofacata- .was quantitatively annalyzed by means of gas chromalyst in theform of a cylinder having 2mm.X 2mm. in size. The reactor was heated ina molten salt bath composed of equalamount mixture of sodium nitrite andpotassium nitrate and maintained at a predetermined temperature.

A gas with the composition cited below was supplied into the reactor ata rate of 10 liter (calculated in terms of NTP) per hour. The reactionpressure was atmospheric one.

Air/ammonia/isobutene=l 7/l.3/1 (molar ratio) The reaction was conductedat a successively varied temperature for 30 min. to 1 hour. The reactiongas tography.

The reaction temperature at which conversion ofisobutene tomethacrylonitrile was maximum and the test results were determined andsummarized inTable.

The contact time in these tests varies from 2.8 to 2.9 seconds.

In the present specification, total conversion of isobutene, conversionto methacrylonitrile and selectivity of methacrylonitrile are defined asfollows:

Total conversion of isobutene Carbon weight of the reacted isobuteneCarbon weight of the supplied isobutcne X (percent) Conversion tomethacrylonitrile Carbon Weight of the formed methacrylonitrile Carbonweight of the supplied isobutenc X 100 (percent) Selectivity ofmethacrylonitrile X 100 (percent) Catalyst 1 A catalyst with theempirical formula Fe W Te Mo Si O was prepared as follows:

Toa solution consisting of ml. of nitric acid (specific gravity 1.38)and ml. of water were added 11.2 g. of electrolytic iron powders to makecomplete solution. Into the resulting iron nitrate solution weredissolved 10.2 g. of metallic tellurium powders. (I)

10.4 g. of ammonium tungstate and 1.8 g. of ammonium molybdate weredissolved in 550 ml. of water. (11) g. of silica sol (SiO 20% by weight)(111) To a mixture of (I) and (III), (II) was added and the resultingmixture was heated to dryness with stirring. The dried mass was brokento pieces and calcined at 200C. for 2 hours and at 400C. for 2hoursfollowed by addition of water and kneading. The resulting mass wasdried at 130C. for 16 hours and calcined at 700C. for 4 hours. Catalyst2 A catalyst with the empirical formula Fe W, Te Mo si o was prepared inaccordance with the method for Catalyst 1. Final calcination wasconducted at 700C. for 4 hours.

Catalyst 3 v A catalyst with the empirical formula Fe w 'le Mo si o wasprepared in accordance with the' method for Catalyst 1. Finalcalcinationwas conducted at 600C. for 4 hours.

Catalyst 4 A catalyst with the empirical formula Fe w Te D- MO Sl O wasprepared in accordance with the method for Catalyst 1. As the startingmaterial for P component was used phosphoric acid. Final calcination wasconducted at 650C. for 4 hours. Catalyst 5 A catalyst with the empiricalformula Fe W Te V- ,Si O,;,, was prepared in accordance 'with the methodfor Catalyst 1, except that ammonium meta-vanadate was used in place ofammonium molybdate. Final calcination was conducted at 600C. for 4hours. Catalyst 6 A catalyst with the empirical formula Fe W Te V- Si Owas prepared in accordance with the method for Catalyst 5. Finalcalcination was conducted at 600C. for 4 hours. Catalyst 7 A catalystwith the empirical formula Fe W- P Mo, 20

Si O was prepared in accordance with the method for Catalyst 1, exceptthat no molybdenum component was added.

Final calcination was conducted at 850C. for 4 hrs. Catalyst 11 Acatalyst having the empirical formula Fe W Te Si O was prepared inaccordance with the method for Catalyst 10. Final calcination wasconducted at 700C. for hours.

Catalyst 12 Final calcination was conducted at 900C. for 2 hours.

Table Results of ammoxidation reaction of isobutene Conver- Selecsion toTotal tivity Composition meth converof meth- Cataof the catalystReaction acrylo sion of acrylolyst (atomic ratio) Calcinationtemperanitrile isobutene nitrile No. Fe W X Me Si conditions ture ('7')(7:) ['Yr] l l 2 Te 4 Mo0.5 30 700C. 4 hrs. 400C. 70 98 71 2 2 l0 10 Te5 Mo 1 50 700C. 4 hrs. 410C. 77 99 78 3 3 10 25 Tel0 Mo 2 30 600C. 4hrs. 410C. 78 100 78 Te 2 4 4 10 10 P 2 M01 50 650C. 4 hrs. 4l0C. 70 9971 5 5 10 2 Te 4 V 1 5O 600C.'4 hrs. 400C. 63 100 63 6 6 10 25 Te10 V l50 600C. 4 hrs. 400C. 67 98 68 7 7 10 P 2 Mo 1 30 600C. 4 hrs. 400C. 6496 67 8 8 10 '20 B 2 Mo 1 30 600C. 4 hrs. 400C. 64 98 65 ComparativeExamples 1 9 10 2 30 900C. 2 hrs. 420C. 42 84 50 Z 0 l0 2 2 30 850C. 5hrs. 430C. 63 95 66 3 ll 10 Te 4 700C. 5 hrs. 430C. 60 94 64 4 l0 2 l 30900C. 2 hrs. 435C. 57 92 62 Si O was prepared in accordance with themethod for Catalyst 1, except that phosphorus component was added inplace of tellurium component. The starting material for the phosphoruscomponent was phosphoric acid.

Final calcination was conducted at 600C. for 4 hours. Catalyst 8 Acatalyst having the empirical formula w w. 13- Mo,Si O, was prepared inaccordance with the method for Catalyst 1, except that boron componentwas added in place of tellurium component. The starting material for theboron component was boric acid.

Final calcination was conducted at 600C. for 4 hrs. Catalyst 9 Acatalyst having the empirical formula Fe, W Si 0 was prepared inaccordance with the method for Catalyst 1. except that none of telluriumand molybdenum components were added.

Final calcination was conducted at 900C. for 2 hrs. Catalyst 10 Acatalyst having the empirical formula Fe, W Te What we claim is:

1. Process for the production of methacrylonitrile from isobutene whichcomprises contacting a mixture of isobutene, molecular oxygen andammonia in the vapor phase at a temperature in the range from 300C. to500C., said mixture having a molar ratio of oxygen- /isobutene from 1/1to 5/1 and a molar ratio of ammonia/isobutene from l/1 to 5/1, with acatalyst consisting of an oxide composition containing the elements inatomic ratio according to the formula Fe W X Me- 0 wherein X representsat least one element selected from the group consisting of phosphorus,boron and tellurium; Me represents at least one element selected fromthe group consisting of vanadium and molybdenum; the subscripts denoteatomic ratio and have the values:

and d is a value corresponding to the oxides formed from the abovecomponents by combination and is 2. Process according to claim 1 whereinsaid catalyst containsfrom 10 to percent by weight ofa silica carrier.

3. Process according to claim 1 wherein the contact time of said mixtureis in the range from 0.1 to 20 seconds.

1 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT N0.3,859,325

DATED January 7, 975 INVENT0R(S) 831120, et 8.1.

II is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Convention date March 21, 1971 shouldread as Merch 12', 1971 Col. 5,line 2, "11'! should read as ."P'"

Signed and sealed this th'day' of May 1975;

(SEAL) Attes'c:

C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officerand Trademarks

1. PROCESS FOR THE PRODUCTION OF METHACRYLONITRILE FROM ISOBUTENE WHICHCOMPRISES CONTACTING A MIXTURE OF ISOBUTENE, MOLECULAR OXYGEN ANDAMMONIA IN THE VAPOR PHASE AT A TEMPERATURE IN THE RANGE FROM 300*C TO500*C, SAID MIXTURE HAVING A MOLAR RATIO OF OXYGEN/ISOBUTENE FROM 1/1 TO5/1, AND A MOLAR RATIO OF AMMONIA/ISOBUTENE FROM 1/1 TO 5/1, WITH ACATALYST CONSISTING OF AN OXIDE COMPOSITION CONTAINING THE ELEMENTS INATOMIC RATIO ACCORDING TO THE FORMULA
 2. Process according to claim 1wherein said catalyst contains from 10 to 90 percent by weight of asilica carrier.
 3. Process according to claim 1 wherein the contact timeof said mixture is in the range from 0.1 to 20 seconds.